// Tencent is pleased to support the open source community by making RapidJSON available.
//
// Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
//
// Licensed under the MIT License (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
// http://opensource.org/licenses/MIT
//
// Unless required by applicable law or agreed to in writing, software distributed
// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
// CONDITIONS OF ANY KIND, either express or implied. See the License for the
// specific language governing permissions and limitations under the License.

#ifndef RAPIDJSON_INTERNAL_META_H_
#define RAPIDJSON_INTERNAL_META_H_

#include "../rapidjson.h"

#ifdef __GNUC__
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(effc++)
#endif
#if defined(_MSC_VER)
RAPIDJSON_DIAG_PUSH
RAPIDJSON_DIAG_OFF(6334)
#endif

#if RAPIDJSON_HAS_CXX11_TYPETRAITS
#include <type_traits>
#endif

//@cond RAPIDJSON_INTERNAL
RAPIDJSON_NAMESPACE_BEGIN
namespace internal {

// Helper to wrap/convert arbitrary types to void, useful for arbitrary type matching
template <typename T>
struct Void {
	typedef void Type;
};

///////////////////////////////////////////////////////////////////////////////
// BoolType, TrueType, FalseType
//
template <bool Cond>
struct BoolType {
	static const bool Value = Cond;
	typedef BoolType Type;
};
typedef BoolType<true> TrueType;
typedef BoolType<false> FalseType;

///////////////////////////////////////////////////////////////////////////////
// SelectIf, BoolExpr, NotExpr, AndExpr, OrExpr
//

template <bool C>
struct SelectIfImpl {
	template <typename T1, typename T2>
	struct Apply {
		typedef T1 Type;
	};
};
template <>
struct SelectIfImpl<false> {
	template <typename T1, typename T2>
	struct Apply {
		typedef T2 Type;
	};
};
template <bool C, typename T1, typename T2>
struct SelectIfCond : SelectIfImpl<C>::template Apply<T1, T2> {};
template <typename C, typename T1, typename T2>
struct SelectIf : SelectIfCond<C::Value, T1, T2> {};

template <bool Cond1, bool Cond2>
struct AndExprCond : FalseType {};
template <>
struct AndExprCond<true, true> : TrueType {};
template <bool Cond1, bool Cond2>
struct OrExprCond : TrueType {};
template <>
struct OrExprCond<false, false> : FalseType {};

template <typename C>
struct BoolExpr : SelectIf<C, TrueType, FalseType>::Type {};
template <typename C>
struct NotExpr : SelectIf<C, FalseType, TrueType>::Type {};
template <typename C1, typename C2>
struct AndExpr : AndExprCond<C1::Value, C2::Value>::Type {};
template <typename C1, typename C2>
struct OrExpr : OrExprCond<C1::Value, C2::Value>::Type {};

///////////////////////////////////////////////////////////////////////////////
// AddConst, MaybeAddConst, RemoveConst
template <typename T>
struct AddConst {
	typedef const T Type;
};
template <bool Constify, typename T>
struct MaybeAddConst : SelectIfCond<Constify, const T, T> {};
template <typename T>
struct RemoveConst {
	typedef T Type;
};
template <typename T>
struct RemoveConst<const T> {
	typedef T Type;
};

///////////////////////////////////////////////////////////////////////////////
// IsSame, IsConst, IsMoreConst, IsPointer
//
template <typename T, typename U>
struct IsSame : FalseType {};
template <typename T>
struct IsSame<T, T> : TrueType {};

template <typename T>
struct IsConst : FalseType {};
template <typename T>
struct IsConst<const T> : TrueType {};

template <typename CT, typename T>
struct IsMoreConst : AndExpr<IsSame<typename RemoveConst<CT>::Type, typename RemoveConst<T>::Type>,
                             BoolType<IsConst<CT>::Value >= IsConst<T>::Value>>::Type {};

template <typename T>
struct IsPointer : FalseType {};
template <typename T>
struct IsPointer<T*> : TrueType {};

///////////////////////////////////////////////////////////////////////////////
// IsBaseOf
//
#if RAPIDJSON_HAS_CXX11_TYPETRAITS

template <typename B, typename D>
struct IsBaseOf : BoolType<::std::is_base_of<B, D>::value> {};

#else // simplified version adopted from Boost

template <typename B, typename D>
struct IsBaseOfImpl {
	RAPIDJSON_STATIC_ASSERT(sizeof(B) != 0);
	RAPIDJSON_STATIC_ASSERT(sizeof(D) != 0);

	typedef char (&Yes)[1];
	typedef char (&No)[2];

	template <typename T>
	static Yes Check(const D*, T);
	static No Check(const B*, int);

	struct Host {
		operator const B*() const;
		operator const D*();
	};

	enum { Value = (sizeof(Check(Host(), 0)) == sizeof(Yes)) };
};

template <typename B, typename D>
struct IsBaseOf : OrExpr<IsSame<B, D>, BoolExpr<IsBaseOfImpl<B, D>>>::Type {};

#endif // RAPIDJSON_HAS_CXX11_TYPETRAITS

//////////////////////////////////////////////////////////////////////////
// EnableIf / DisableIf
//
template <bool Condition, typename T = void>
struct EnableIfCond {
	typedef T Type;
};
template <typename T>
struct EnableIfCond<false, T> { /* empty */
};

template <bool Condition, typename T = void>
struct DisableIfCond {
	typedef T Type;
};
template <typename T>
struct DisableIfCond<true, T> { /* empty */
};

template <typename Condition, typename T = void>
struct EnableIf : EnableIfCond<Condition::Value, T> {};

template <typename Condition, typename T = void>
struct DisableIf : DisableIfCond<Condition::Value, T> {};

// SFINAE helpers
struct SfinaeTag {};
template <typename T>
struct RemoveSfinaeTag;
template <typename T>
struct RemoveSfinaeTag<SfinaeTag& (*)(T)> {
	typedef T Type;
};

#define RAPIDJSON_REMOVEFPTR_(type)                                                                                    \
	typename ::RAPIDJSON_NAMESPACE::internal::RemoveSfinaeTag<::RAPIDJSON_NAMESPACE::internal::SfinaeTag&(*)type>::Type

#define RAPIDJSON_ENABLEIF(cond)                                                                                       \
	typename ::RAPIDJSON_NAMESPACE::internal::EnableIf<RAPIDJSON_REMOVEFPTR_(cond)>::Type* = NULL

#define RAPIDJSON_DISABLEIF(cond)                                                                                      \
	typename ::RAPIDJSON_NAMESPACE::internal::DisableIf<RAPIDJSON_REMOVEFPTR_(cond)>::Type* = NULL

#define RAPIDJSON_ENABLEIF_RETURN(cond, returntype)                                                                    \
	typename ::RAPIDJSON_NAMESPACE::internal::EnableIf<RAPIDJSON_REMOVEFPTR_(cond),                                    \
	                                                   RAPIDJSON_REMOVEFPTR_(returntype)>::Type

#define RAPIDJSON_DISABLEIF_RETURN(cond, returntype)                                                                   \
	typename ::RAPIDJSON_NAMESPACE::internal::DisableIf<RAPIDJSON_REMOVEFPTR_(cond),                                   \
	                                                    RAPIDJSON_REMOVEFPTR_(returntype)>::Type

} // namespace internal
RAPIDJSON_NAMESPACE_END
//@endcond

#if defined(__GNUC__) || defined(_MSC_VER)
RAPIDJSON_DIAG_POP
#endif

#endif // RAPIDJSON_INTERNAL_META_H_
